This proposal is devoted to studies of the immune properties of large vessel endothelium and smooth muscle. Studies are designed that will determine the ability of large vessel smooth muscle and endothelium to activate, stimulate proliferation of, and present antigen to various subtypes of T lymphocytes; to determine whether aortic smooth muscle supports in vitro proliferation of granulocytes and produces message for colony stimulating factors; to characterize immunologically important cytokine-inducible targets on large vessel smooth muscle and endothelial cells; and to correlate the morphologic properties and growth characteristics of smooth muscle cells with immune functions. It has been increasingly appreciated that large vessel smooth muscle and endothelium interact with lymphocytes in many different ways. Numerous studies have been devoted to determination of the effects of lymphocyte-secreted cytokines on smooth muscle and endothelium. The thrust of this study will be the opposite, mainly to determine the effects of smooth muscle and endothelium on lymphocytes and granulocytes. The key questions and hypotheses underlying these proposed studies are derived in part from recent studies in which we have shown that microvascular smooth muscle is a good antigen presenting cell under our conditions and also supports the colony proliferation of granulocytes in vitro. Microvascular smooth muscle also differs considerably from microvascular endothelium in that each activates different subsets of lymphocytes and under different respective conditions. It will be important to determine whether large vessel smooth muscle, which is normally involved in the atherosclerotic process, possesses similar or different immunologic properties from that of microvascular smooth muscle.